This invention relates to the measurement of particulate adhered to elastomeric articles such as gloves, and the cleaning of the particulate from the articles.
Electronic devices such as microcircuits are fabricated and assembled inside clean rooms. Any particulate matter in the air may come to rest on the electronic devices, causing electrical shorts and otherwise rendering the devices inoperable. The air entering the clean room is therefore filtered to remove the airborne particulate matter. However, such filtering is not entirely without adverse consequences, inasmuch as it increases the static electricity in the clean room, which in turn tends to cause any airborne particulate to adhere to the electronic devices.
The workers in the clean room wear elastomeric gloves made of natural latex or synthetic elastomers to prevent contact of the skin of their hands to the electronic devices. The gloves are cleaned and packaged by glove manufacturers or laundries, but become contaminated with particles during shipping and storage. Elastomeric gloves are subject to surface hardening and microcracking. The microcracking allows particulate matter to be created and/or trapped at the microcracks. The particulate matter may later detach from the microcracks and surfaces of the gloves, and thence possibly reach the surfaces of the electronic devices.
The workers therefore change their gloves on a regularly scheduled basis, typically about every 30-60 minutes, whether or not the gloves have become contaminated with particulate matter. The regular changing of the gloves is meant to ensure that particulate-contaminated gloves are not used in the clean room operations. To change gloves, the workers leave the clean room, go to a donning room, remove the old gloves, don new gloves, and return to the clean room to work. This changing of the gloves typically entails 5-10 minutes of lost labor per hour for each worker.
Many electronic device fabrication processes performed inside clean rooms experience high scrap rates (i.e., low product yields) in part because of particulate contamination from items such as the gloves worn by the workers. The regular changing of the gloves in the clean room represents a significant addition to the cost of the electronic devices, both in the cost of the multiple pairs of gloves worn by the workers and in the lost labor time. However, experience has shown that the failure to change the gloves on this regular schedule results in significantly reduced product yields in the manufacturing operation due to particle contamination of the electronic devices. Current technology does not allow frequent testing and correlation of glove cleanliness to product yields.
Medical and dental personnel face a similar problem in their need to change elastomeric gloves on a regular basis. Even when working on a single patient, the medical and dental personnel must often change gloves several times, to avoid contamination of machinery and instruments.
There is a need to reduce the costs associated with the regular changing of gloves in clean room, medical, laboratory and other environments where particulate contamination must be avoided. The present invention fulfills this need, and further provides related advantages.
The present invention provides an apparatus and method for measuring the particulate content found on the surfaces of elastomeric articles such as gloves, and for reducing the particulate content to acceptable levels in the event that they are too high. The apparatus may be readily used in clean room, medical, laboratory, and other environments. The approach of the invention reduces the need to change gloves on a regular basis or, alternatively, increases the time between required changing of the gloves. The apparatus may also be used to monitor the number of times each worker changes gloves, and to correlate the changing of gloves with manufacturing yields. It also may be used to sterilize the glove of life forms, where sterilization is important such as in a medical or laboratory setting.
In accordance with the invention, an apparatus for processing an elastomeric article comprises an enclosure having a gas-filled interior, a support that supports the elastomeric article within the enclosure at an article support location, and a source of a gaseous cleaning agent operable to introduce a gaseous flow of the gaseous cleaning agent into the interior of the enclosure to flow past the article support location and to contact the elastomeric article. The cleaning agent is operable to dislodge a particulate contaminant from the elastomeric article and entrain the particulate contaminant in the gaseous flow as it passes by the elastomeric article. An exhaust port is positioned to receive the gaseous flow after it has passed by the elastomeric article. A particle counter measures particles in the gaseous flow after it has passed by the elastomeric article, and preferably after it has passed through the exhaust port.
The source of the gaseous cleaning agent desirably comprises a source of a vaporized cleaning material, such as nebulized EDTA, isopropyl alcohol, oxalic acid, or hydrogen peroxide, and a weakly ionized plasma source disposed within the interior of the enclosure and proximate to the article support to create a weakly ionized plasma in the ambient atmosphere adjacent to the article support. The weakly ionized plasma is of relatively low ionization energy so that the plasma does not harm the elastomeric article or a human being who may be wearing the elastomeric article during processing.
The elastomeric article and/or the gaseous cleaning agent may optionally be mechanically pressure pulsed during the processing. The pulsing action further aids in dislodging particulate from the elastomeric article.
The particulate matter is dislodged from the elastomer by the combined action of the vaporized cleaning material and the weakly ionized plasma source, and optionally by the mechanical pulsing. The particulate is entrained into the gas flow, and flows out of the enclosure through the exhaust port. The particle counter measures the amount of particulate in the gas flow, as a measure of the particulate on the elastomeric article initially and also during and after processing. If the processing successfully reduces the particulate content to an acceptable level, the elastomeric article may be placed back into service. The particle counter also allows the automatic recording of the time and results of particle tests for product scrap correlation. Such recording may be done on any data acquisition system such as a personal computer. In the context of an elastomeric glove, the glove may be reused, and the worker does not need to change gloves.
The removal of particulate matter is sufficient for many situations. In others, such as medical and laboratory facilities, it is also necessary to sterilize the elastomeric article by removal or destruction of living microorganisms. In that case, the enclosure may also be provided with a microorganism sterilizer disposed within the interior of the enclosure and proximate to the article support location.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.